“Reducing fuel consumption and noise levels in commercial jet engines.”

Context & Issue

Most commercial aircraft are powered by turbojet engines.

The current trend for future turbojet engines is towards even higher bypass ratios. These UHBR (Ultra-High Bypass Ratio) engines have large fans running at relatively low speeds. As a result of these lower speeds, fuel consumption can be reduced.

Another consequence is that the engine’s noise signature is modified. Engine and fan noise will be reduced; core noise will become more significant.

In this context, the CIRRUS project aims to validate advanced low-noise concepts by developing advanced numerical and experimental tools, in order to reduce the background noise of future UHBR 2030+ turbojet engines.



Improve numerical methods for predicting noise source mechanisms and sound radiation from the acoustic core


Improve experimental methods for measuring the background noise contribution of real engines


Develop, test and integrate new generations of acoustic noise reduction coatings in ceramic matrix composites (CMC)


Study the influence of future UHBR 2030+ architectures on main noise sources by comparing different turbines

Key Development Points


The first part of the project is devoted to improving basic noise prediction tools by implementing an industrial LES/CAA workflow.


A second part focuses on experimental activities, with the development of post-processing methodologies to identify the main noise contribution.


The third part of the project focuses on noise reduction concepts. CMC coating concepts will be studied and tested.


Finally, relevant noise reduction concepts will be evaluated on a full-scale UHBR. Measurements and simulation results will be compared to qualify numerical means up to TRL6.

Project Ambitions

Bypass ratio is one of the main indicators of turbofan efficiency. Ultra-high bypass ratio (UHBR) engines have large fans that run at relatively low speeds and therefore consume less fuel. Although high bypass ratios generate lower jet and fan noise, core noise increases.

The EU-funded CIRRUS project will combine numerical simulations and experimental work to reduce core noise for future UHBR 2030+ turbofan engines.

Another part of the work will focus on the development of acoustic coatings based on ceramic matrix composites. The proposed noise reduction concepts will be tested in real engines. Experimental measurements will be compared with theoretical ones to bring the proposed technologies to a high level of maturity (Technology Readiness Level 6).

Key Figures

3,6 M€



months of work


scientific publications


The project behind this application has received funding from the CleanSky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation program, under grant agreement no. 886554.